What SAR Is

SAR stands for Specific Absorption Rate. It measures the rate at which radio frequency energy is absorbed by body tissue, expressed in watts per kilogram (W/kg). When your phone transmits — calling, texting, loading a page, syncing in the background — it emits RF energy. Some of that energy is absorbed by your body. SAR quantifies how much.

The FCC requires every phone sold in the U.S. to have a SAR value at or below 1.6 W/kg, measured over 1 gram of tissue. The European limit is 2.0 W/kg, measured over 10 grams of tissue. These numbers sound precise. They are precise — for the specific conditions under which they’re measured. Those conditions bear little resemblance to your actual phone use.

How SAR Is Tested

The test uses a physical model called a SAM (Specific Anthropomorphic Mannequin) — a standardized plastic shell filled with liquid that simulates the electromagnetic properties of human tissue. The phone is placed at a specific distance from the mannequin’s head or body, set to transmit at maximum power, and a probe measures RF absorption at various points inside the liquid.

The test produces a single number: the highest absorption measured at any point, averaged over 1 gram (FCC) or 10 grams (EU) of simulated tissue. This is the SAR value printed in your phone’s documentation.

The test has several characteristics that are worth understanding.

The SAR test is a regulatory compliance exercise. It ensures that a phone, under specific controlled conditions, does not exceed a defined absorption threshold. It does not measure your actual exposure. It does not account for how you carry your phone, how long you use it, how many bands transmit simultaneously, or the specific absorption characteristics of your anatomy.

What the Number Means (And Doesn’t Mean)

A lower SAR number does not necessarily mean less exposure. SAR is measured at maximum transmit power. A phone with a lower SAR at maximum power might spend more time at high power (due to poor antenna design) than a phone with a higher SAR that dynamically manages power more efficiently. The number on the spec sheet is a ceiling, not an average.

The FCC limit is not a safety threshold. The 1.6 W/kg limit was set with a safety margin relative to levels that cause thermal effects in animal studies. It is not based on a finding that 1.6 W/kg is safe and 1.7 W/kg is dangerous. It is an engineering margin applied to a thermal model. As Dispatch #008 documented, the thermal model does not evaluate non-thermal biological effects.

SAR does not measure cumulative exposure. You absorb RF energy from your phone for the entire time it’s powered on and in proximity to your body. SAR measures peak instantaneous absorption. The total energy your body absorbs over a day, a month, or a decade is not captured by the SAR number.

SAR is frequency-dependent. Different frequencies penetrate tissue differently. Lower frequencies (600–900 MHz) penetrate deeper into tissue. Higher frequencies (mmWave 5G at 24–47 GHz) are absorbed primarily in the skin. A phone that scores well at cellular frequencies may have different absorption characteristics at WiFi or millimeter-wave frequencies. The SAR number does not distinguish.

How to Find Your Phone’s SAR

The Distance Variable

Of all the gaps between the SAR test and reality, distance is the most significant. RF absorption follows the inverse square law — doubling the distance reduces exposure by approximately 75%. Halving the distance increases exposure by approximately 400%.

When your phone is in your pocket, the distance between the antenna and your body is effectively zero. When the SAR test was conducted, the distance may have been 5–15mm. That difference translates to substantially higher actual absorption than the tested value.

This is not a theoretical concern. Phone manufacturers include fine-print RF exposure guidelines in their documentation that specify minimum separation distances. Apple’s iPhone documentation has historically recommended keeping the device at least 5mm from the body during wireless transmission. Most people have never read this recommendation. Fewer have followed it.

The simplest way to reduce RF absorption from your phone is to increase the distance between the phone and your body. A table rather than a pocket. A speakerphone rather than the device against your ear. Or — for the times when you want the device completely silent on the network — a Faraday pouch that eliminates transmission entirely.

What This Means for You

The SAR rating is a data point, not a verdict. It tells you the maximum absorption under controlled test conditions. It doesn’t tell you your actual daily exposure, whether that exposure has biological effects, or whether the thirty-year-old safety standard governing it is adequate for the modern electromagnetic environment.

What it does tell you is that your phone produces measurable RF absorption in human tissue. That absorption is real, quantified, and varies with distance, power, frequency, and duration. The regulatory framework that governs it was built for a different era. And the research that would definitively characterize the biological implications of chronic, close-proximity, multi-band exposure has not been conducted at the scale required to settle the question.

You don’t need to be alarmed by your SAR number. You do need to understand what it actually represents — and what it doesn’t. Informed decisions require information. This dispatch is that information.